public int NegaMax(TicTacToeBoard game, Marker player, int depth)
{
int maxScore = -1;
int sign = 1;
if (game.CheckForWinner(game.Board, Marker.X)) // return score/move
{
return(StaticEvaluation(Marker.X));
}
else if (game.CheckForWinner(game.Board, Marker.O))
{
return(StaticEvaluation(Marker.O));
}
else if (game.CheckForDraw(game.Board)) //return score/move
{
return(StaticEvaluation(Marker.Blank));
}
if (player != Marker.X)
{
sign = -1;
}
List <Vector2> moves = game.FindBlankCells(game.Board);
TicTacToeBoard gameCopy = new TicTacToeBoard();
int score = 0;
foreach (Vector2 nextMove in moves)
{
gameCopy.Board = gameCopy.CopyBoard(game.Board);
gameCopy.PlaceMarker(gameCopy.Board, player, nextMove);
score = sign * NegaMax(gameCopy, gameCopy.GetOppositeMarker(player), depth + 1);
if (score > maxScore)
{
maxScore = score;
}
}
return(maxScore * sign);
}
public void PlayTicTacToe( )
{
if (IsGameover == false)
{
if (p1_X == null || p2_O == null)
{
return;
}
if (p1_X.IsTurnActive == true)
{
if (timed == false)
{
t = turnDelay + Time.time;
timed = true;
}
if (Time.time < t)
{
return;
}
timed = false;
TicTacToeMove bestMove = null;
if (isSearching == false)
{
bestMove = p1_X.NegaMaxMove(board); // NEGAMAX tree-search
isSearching = true;
}
if (bestMove != null)
{
FireRandomScribbleSFX( );
boardState[(int)bestMove.Cell.x][(int)bestMove.Cell.y] = Marker.X;
cells[bestMove.Cell].GetComponent <SpriteRenderer>().sprite = Resources.Load <Sprite> (ResourcePath.x);
p1_X.IsTurnActive = false;
p2_O.IsTurnActive = true;
if (board.CheckForWinner(boardState, Marker.X))
{
GameWinner = "You lost!";
WinningCoordinates = board.WinningCoordinates;
IsGameover = true;
}
if (board.CheckForDraw(boardState))
{
GameWinner = "A draw - better than losing.";
WinningCoordinates = null;
IsGameover = true;
}
isSearching = false;
}
else
{
Debug.Log("AI is searching for a move ... ");
return;
}
}
else if (p2_O.IsTurnActive == true)
{
GameObject clicked = p2_O.ClickHandler <Grid2DVertexComponent> ( );
if (clicked == null)
{
return;
}
Vector2 m = clicked.transform.position;
if (boardState[(int)m.x][(int)m.y] == Marker.Blank) //move success
{
FireRandomScribbleSFX( );
boardState[(int)m.x][(int)m.y] = Marker.O;
clicked.GetComponent <SpriteRenderer> ( ).sprite = Resources.Load <Sprite> (ResourcePath.o);
if (board.CheckForWinner(boardState, Marker.O))
{
GameWinner = "You won!";
WinningCoordinates = board.WinningCoordinates;
IsGameover = true;
}
if (board.CheckForDraw(boardState))
{
GameWinner = "A draw - better than losing.";
WinningCoordinates = null;
IsGameover = true;
}
p2_O.IsTurnActive = false;
p1_X.IsTurnActive = true;
}
}
}
else
{
Debug.Log("GAMEOVER");
}
}